This invention relates generally to the design of an improved delivery system for applying adhesives. More particularly, the delivery system includes a pair of syringes, each with a plunger which when activated results in the combining of fluids in the syringes. The fluids, which are stored separately, are applied to a surface such as a treatment site as a stream. Although useful for any adhesive made from at least one solution, the delivery system is useful for combining tissue adhesive components such as a first solution of fibrinogen and a second solution of thrombin. Upon contact with one another, these two solutions undergo a rapid chemical reaction which causes coagulation into a functional tissue adhesive. Thus, it is desired to keep these two solutions separately confined until just prior to the time of direct application on a patient and then thoroughly and rapidly mix them for treatment of a wound.
The treatment of wounds on patients typically involves suturing or covering the wound with an external dressing. There are some applications, however, where the external dressing or sutures are not effective or even act as an irritant. In situations such as treatment of internal body cavities, it has been discovered that treatment of the wound with the body's own healing compounds has been very effective in inducing wound closure and subsequent healing. A common method of treating these wounds takes advantage of the rapid reaction which occurs when a solution of clotting factors, such as fibrinogen, comes into contact with a solution of a catalyst, such as thrombin, to form a complex which acts as a tissue adhesive. This rapid reaction typically commences within a few seconds after the solutions initially contact one another, and it typically attains a soft set after several more seconds of contact. A common name for such a complex is fibrin glue.
These fibrin glues have been known in the medical field for many years. U.S. Pat. No. 2,533,004 which issued on Dec. 5, 1950 to John D. Ferry discloses mixing varying concentrations of fibrinogen with thrombin to create fibrin clots.
Typical fibrin glue delivery systems either externally or internally mix the fluids. Internal mixing generally takes place in a mixing chamber where the amount of time the mixed solution remains in the mixing chamber is minimized. This minimization must occur so that the fibrin glue does not set up or coagulate within the mixing chamber and result in clogging of the chamber.
An internal mixing chamber is disclosed in U.S. Pat. No. 4,978,336, issued on Dec. 18, 1990 to Capozzi, et al. The syringe system of U.S. Pat. No. 4,978,336 has first and second syringes containing proteins which when mixed become a tissue adhesive. A manifold locks onto the two syringes. The manifold receives the output stream from each syringe and delivers the streams to an output nose. Detachably locked onto the output nose is a needle or spray nozzle. Mixing of the proteins either occurs within the lumen of the needle or within a mixing space provided within the output nose. The mixed combination is ejected from the either the needle or a spray outlet on the output nose resulting in application of the mixture to a wound.
Numerous devices with similar mixing chambers are known in the art. However, these devices typically all present similar problems. One of the problems is if the syringe plungers are depressed at a very slow rate, the reacting mixture is not evacuated from the system quickly enough and clotting can occur within the output nose or needle or within the mixing chamber. Thus, it has been found that for quick reacting substances, such as fibrin glue components, it is desired to have a method for uniform mixing that is not dependent on the rate at which the user introduces the solutions into the mixing chamber.
An additional problem which is characteristic of mixing chamber systems in which mixing occurs within the device is that this rapid reaction, once started, can coagulate backwards or upstream through the entire system and into at least one of the syringes containing the solutions of clotting factors. Thus, forward flow through the device must exceed the rate at which the reaction can coagulate backwards or upstream. Unless the user has been made aware that this can occur, he may be unaware of the minimum rate at which he should depress the syringes to counteract this tendency.
A number of devices exist which mix the components outside of the device thereby eliminating clotting within the mixing chamber. These devices typically use overlapping contact of airborne sprays or streams to obtain mixing. The apparatus utilized typically includes a fibrinogen solution stored separately from a thrombin solution, where these two solutions are mixed either immediately prior to or upon application on a wound, but in either case external to the device.
An example of a delivery system based on the mixing of overlapping jets of airborne particles is provided in U.S. Pat. No. 4,874,368, which was issued on Oct. 17, 1989 to Miller, et al. The delivery system disclosed in U.S. Pat. No. 4,874,368 provides a two syringe apparatus which enables the two solutions to stream from a sprayer and mix upon application over a wound. A connecting clip member is fitted on each of the piston-type plungers inserted into each syringe. The tip of each syringe is fitted with a specially formed needle, bent to receive the initially parallel outflow from each syringe. The bend in each needle redirects the outflow through a hollow plastic sleeve which serves as a retainer for the long, parallel needle tips. These tips extend slightly beyond the distal end of the hollow sleeve. As solution exits each tip, it is propelled into a spray or stream. The trajectories of the sprays partially overlap and begin mixing either while airborne or as they strike the surface being treated. The clotting reaction commences as the solutions contact one another. The close positioning of the needle tips to each other may result in spray from one tip coming to rest at the orifice of the other tip, which if the apparatus is temporarily not being used by the surgeon, may result in the clotting reaction proceeding upstream into the confines of the needle. This will result in the system being plugged and any further use of the device typically being prohibited.
It is accordingly a principle object of the present invention to provide a new and improved fluid delivery system which permits rapid and complete blending of two solutions thereby resulting in the formation of fibrin glue while prohibits clotting within the delivery system when the system is temporarily not being used by the surgeon.